1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an inductive electromagnetic transducer, a method of manufacturing the same, a head gimbal assembly, and a hard disk drive.
2. Related Background Art
In recent years, the areal density in hard disk drives has been increasing remarkably. Recently, the areal density in hard disk drives has reached 160 to 200 GB/platter in particular, and is about to increase further. Accordingly, thin-film magnetic heads have been required to improve their performances.
Widely used as a thin-film magnetic head is a combination thin-film magnetic head having a structure in which a recording head including an inductive electromagnetic transducer for writing and a reproducing head including a magnetoresistive device (which will also be referred to as MR device in the following) for reading are laminated.
In this kind of combination thin-film magnetic head, the recording head generally comprises a medium-opposing surface (air bearing surface, which will also be referred to as ABS), a lower magnetic pole layer, an upper magnetic pole layer, a recording gap layer, and a thin-film coil. The lower and upper magnetic pole layers have respective magnetic pole parts opposing each other (opposing magnetic pole parts) on the side of the medium-opposing surface, and are magnetically connected to each other by a connecting part disposed at a position separated from the opposing magnetic pole parts. The recording gap layer is formed between the opposing magnetic electrode parts. The thin-film coil is insulated from the lower and upper magnetic pole layers, while being at least partly disposed therebetween.
For improving performances of a recording head, its recording density in particular, a recording medium is required to improve its track density. This makes it necessary to realize a recording head having a narrow track structure in which the track width, i.e., the width between the two opposing magnetic pole parts in the medium-opposing surface, is reduced to a size of several microns to submicrons. Therefore, recording heads have been made by utilizing semiconductor processing technologies.
As the track width decreases, it becomes harder for a recording head to generate a magnetic flux having a high density between two opposing magnetic pole parts. Therefore, it has been desired to use a magnetic material having a high saturated magnetic flux density as a material for the magnetic pole parts.
When the frequency of a recording signal rises as the recording density improves, on the other hand, the recording head is required to improve the rate at which the magnetic flux changes, i.e., shorten the flux rise time. It is also desirable for the recording head to lower the deterioration in recording characteristics such as overwrite characteristic and non-linear transition shift in a high-frequency band.
For improving recording characteristics in a high frequency band, it is desired that the magnetic path length of the recording head be reduced so as to be able to follow rapid changes in recording signals which are likely to change fast while having a high frequency. The magnetic path length is mainly determined by the length (hereinafter referred to as “yoke length”) from the medium-opposing surface in the lower or upper magnetic pole layer to the connecting part, whereby reducing the yoke length is effective at shortening the magnetic path length. When the thin-film coil is wound between the medium-opposing surface and the connecting part, reducing the pitch of windings disposed between the medium-opposing surface and the connecting part (hereinafter referred to as “winding pitch”) in the windings of the thin-film coil is effective at shortening the yoke length.
Conventional thin-film magnetic heads are roughly divided into those having a planar spiral thin-film coil wound about a connecting part (see the following Patent Document 1), and those having a thin-film coil helically wound about at least one of the lower and upper magnetic pole layers (see the following Patent Documents 2, 3, 4).
The former thin-film magnetic heads generate a large part of magnetic fluxes near the connecting part, in which the magnetic fluxes guided to the opposing magnetic pole parts by the lower and upper magnetic pole parts are used for recording information. However, since most of magnetic fluxes are generated about the connecting part, only about a few percent of the generated magnetic fluxes are used for recording, whereby the recording with magnetic fluxes has not been effected efficiently in the former thin-film magnetic heads. Therefore, the number of turns of the thin-film coil has been made as large as possible in order to increase magnetic fluxes used for recording in the former thin-film magnetic heads. Conventionally known as an example of techniques therefor is one in which, between windings of a first coil, windings of a second coils are disposed, so as to reduce the winding pitch (see the following Patent Document 5).
In the latter thin-film magnetic heads, the thin-film coil is disposed near the medium-opposing surface, whereby generated magnetic fluxes are used for recording more efficiently than in the former. Therefore, as compared with the former thin-film magnetic heads having a planar spiral thin-film coil, the latter thin-film magnetic heads can decrease the number of turns of the thin-film coil, thereby being more advantageous in reducing the yoke length.
Reducing the yoke length is effective in improving recording characteristics in a high-frequency band in the latter thin-film magnetic heads as well, for which it will be advantageous if the winding pitch of the thin-film coil is made as small as possible. Raising the number of turns in the thin-film coil is also effective in increasing magnetic fluxes used for recording. For realizing all of them, it is necessary for the winding pitch to be made as small as possible, so as to reduce the yoke length and allow the number of turns in the thin-film coil to increase. To this aim, the width of each turn (turn width) of the thin-film coil is required to narrow.
Narrowing the turn width in the thin-film coil increases the ohmic value of the thin-film coil, thereby enhancing the heat generated from the thin-film coil. When the heat generated from the thin-film coil increases, the magnetic pole parts are more likely to project toward the recording medium, thereby colliding with the recording medium. Therefore, the conventional thin-film magnetic heads have not been able to reduce the turn width so much, and thus have failed to decrease the yoke length.
Conventionally, the thin-film coil has been formed by frame plating. Frames used in frame plating have wall parts to be disposed between turns. Each wall part must have a certain extent of width in order to maintain its form. This makes it difficult to reduce the space between adjacent turns (turn space) when forming the thin-film coil by frame plating. Though the technique disclosed in the following Patent Document 5 can reduce the space between adjacent turns, the resulting thin-film magnetic head comprises a planar spiral thin-film coil, and thus is disadvantageous in that generated magnetic fluxes cannot efficiently be used for recording.
Patent Document 1: U.S. Pat. No. 6,043,959
Patent Document 2: U.S. Pat. No. 5,995,342
Patent Document 3: Japanese Patent Application Laid-Open No. 2000-311311
Patent Document 4: U.S. Pat. No. 6,459,543B1
Patent Document 5: U.S. Pat. No. 6,191,916B1